1. Field of the Invention
The present invention relates to a light source device, an optical scanning device, and an image forming apparatus.
2. Description of the Related Art
In recent years, in an image forming apparatus such as a laser printer and a digital copying machine, there is an increasing demand for high-speed and high-density printing. A semiconductor laser is generally employed as a light source, and recently, a vertical cavity surface emitting laser (hereinafter, “VCSEL”) has been used in addition to an edge emitting semiconductor laser that was used more commonly.
On the other hand, with the advancement of the high-speed and high-density printing, the heating value generated in a drive circuit that supplies a drive signal to the light source tends to increase. The drive circuit is provided normally near the light source to suppress the delay of the drive signal. If the temperature of the light source increases due to the heating of the drive circuit, this may shorten the lifetime of the VCSEL because the VCSEL is weak against heat compared with the edge emitting semiconductor laser, and cause degradation of the image quality.
For example, Japanese Patent Application Laid-open No. 2001-217366 discloses a cooling device for circuit parts. The cooling device is configured to lead heat from heating parts on a circuit board to the outside of the circuit board by means of a heat pipe and radiate heat by a heat radiation unit composed a radiating fin arranged on the heat radiation side of the heat pipe and a fan, thereby efficiently radiating heat out of the device. The cooling device has drastically increased the cooling efficiency while decreasing the heights of the cooling parts.
Japanese Patent Application Laid-open No. 2002-271073 discloses a cooling device that makes it possible to exhaust heat on a circuit board on which highly heating parts such as a microprocessor unit are mounted and cool other heating parts by one cooling fan.
Japanese Patent Application No. 4087133 discloses a cooling structure of an electronic circuit board on which a sink having a fan is mounted for the main heating element.
However, the cooling devices disclosed in Japanese Patent Application Laid-open No. 2001-217366, Japanese Patent Application Laid-open No. 2002-271073 and Japanese Patent Application No. 4087133 become large in size, which is disadvantageous.